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Topic Review (Newest First)

07-31-2007 11:32 PM

robrichtx

Gas vs. Diesel

I have a Catalina 27 with an Atomic 4, a Beneteau 32s5 with a Volvo M2002 diesel, two Jetta TDI turbocharged diesels, and an air cooled flat six gas sports car.

I do 90 percent of the maintenance on all the engines and have 100's of hours behind each of them. When it comes to the marine engines, I have actually had a harder time keeping the diesel running than the Atomic 4. Gasoline, with proper fuel additives (PRI-G) will keep for years. Diesel, on the other hand, will tend to grow algae/fungi (ask me how I know...). That said - each engine has its quirks, but none of those quirks are very difficult to understand. I am not a mechanic, either - I just like knowing my engine is there when I need it. And I really like both the Atomic and the Volvo.

So - don't let gas or diesel influence your decision. A mild dose of reason and intelligence will keep you safe and sound with either route.

Focus instead on the condition of the engine in question - its compression, ease of start, and state of engine systems. Pick an engine that is either in very good condition, or one that can be rebuilt quickly w/new parts (Atomic 4 is great for that) and brought current.

Rob

03-30-2007 12:16 AM

Valiente

Fair enough, I have seen a few otherwise undamaged cars catch fire due to some flaw in the fuel system. By contrast, in my limited boat owning career (1999 to present), I have seen two sailboats sink at dock due to hose clamp failure/backsiphoning of the head intake. Neither was lost, but some upholsterers were made richer.

I saw a third boat take on water because of a clamp or hose failure (everyone was too embarrassed to admit it) on a C&C 35. Ironically, it had an Atomic 4 and furthermore, once some bright sailor had figured out the floorboards were floating and had shut off the seacock, they used the Atomic 4 raw water hose (presumably loose at this point) to suck the boat 90% dry. The Atomic 4 was undamaged by this, so I assume they didn't have a lot of particulate crap in their bilges.

Risk is everywhere, but frequently the amount of actual risk is really about managing negligence and/or ignorance.

03-29-2007 10:58 PM

Boasun

Sorry but in my extensive sea going career (1958 to present), I have seen three Gas powered launches/cabin cruisers blow up... Sorry Diesel only in my books.

02-19-2007 11:43 PM

Sailormann

There are thousands of boats out there with Atomic IV inboard gasoline engines that have run well for more than twenty years. Many, many more than have ever blown up. They are not as safe as a diesel, but they are far quieter, If you are intelligent and careful, you won't have a problem. Outboards are the least reliable option. And don't worry too much about your motor. I sailed a 30 foot schooner for years. The engine died about six months after I bought the boat and I didn't have the money to fix it, then realised I didn't need it. Never fixed it, never missed it.

01-06-2007 09:19 PM

marinesniper

808state:

I live in Aventura Florida, 20 min north of downtown Miami.

I bought a 30ft Lippincott with an 15hp diesel engine. It was listed for 15k but I paid 9.2k out the door. it is 20 years old and needed TLC...mostly engine repair on the fuel side of things.

I believe the market for sail boats in Miami is soft and you can get a better boat for 10k if you negotiate good...I found alot of people are willing to come down thousands off the first price.

Just my opinion...!

12-18-2006 07:59 PM

seabreeze_97

Another angle on things that makes me prefer diesel is the way we get jerked around regarding gas. In a pinch, the trucks and ships have to run. Diesel will have production priority over gas. Post -Katrina is a perfect example. Couldn't get gas, then after a few days, only a $20 limit (about 6 gallons!), but you could have all the diesel you wanted. Also, while gas engines will run on ethanol, the conversion requires anti-corrosion mods, but diesels run on bio-diesel will little or no adjustments, even used cooking oil will work with a simple "greasel" kit. Granted, this isn't as big a deal with pleasure craft, but still something to consider.

12-18-2006 05:07 PM

gc1111

Talk about legs! Did anyone notice the timestamps on the entries on this thread?
I have owned both gas and diesel inboards. Both are quite reasonable, but you have to have a different set of operating habits for each.
I have never met a cruising sailor that was happy with an outboard in open water. When you start pitching in a seaway you lose the propulsion just when you need it. Also most outboards can't handle the battery charging that a cruising boat needs. Leave the outboards to the racers to get back into their slips.

12-18-2006 04:03 PM

feetup

Gas or Diesel

If well looked after there will be no more problems with one or the other. If left to rot both will bite you.
Dirty gas will plug a filter, as will diesel. Water in the fuel will cause a gas engine to quit, repairable with some methanol and perhaps draining the float bowl. If water get's past the filtering system of a diesel it will destroy the pump, and most likely blow the tips off the injectors since the pressure required to atomize diesel fuel (about 14,000 psi) is enough to cause severe mechanical damage to the system trying to force the relatively high surface tension of water through holes that are almost too small to see. Here again the cost issue comes out. A carburetter and distributor rebuild (which you can most likely do yourself) is really cheap compared to a diesel injection pump/ injector rebuild/exchange. Also diesel fuel and everything it touches stinks. Moreover diesel fuel will grow a filter plugging organism extremely quickly if conditions are right rendering the fuel and all components of the system useless.
That being said, diesel, with a clean fuel system and semi regular oil changes will cause very few problems, and clatter away for a long, long time.
The higher BMEP (Brake mean effective pressure) of a diesel, combined with the higher calorific value of the fuel, and more importantly the fact that diesel fuel will burn in the cyl. no matter how little of it is injected mean better potential economy. Gasoline needs to be mixed with air at a very specific ratio, (called the stoiocheometric ratio, about 15:1 air/fuel by mass) in order to burn. Generally primative carburation systems lean toward the rich side in order to assure combustion and to keep the threat of detonation low at all throttle settings. Diesel injects a specific metered amout of fuel each cycle, dictated by the the RPM the governor is set to achieve. (If the engine cannot achieve the RPM that the governor is set at because of loading then the pump will run at full rack, injecting as much fuel each cycle as the the pump is able whether or not the engine can burn it competely or not, passing the unburned fuel out the exhaust as black smoke/soot. The point being that if operated below the tourque peak a diesel will always be more efficient than gasoline. I'm not sure if fuel savings alone would ever equal the much higher initial cost or rebuild cost. Diesels are, of neccessity built more robustly and hence can expect a long life. The Atomic 4 was designed with very low component loadings so it too can expect a long life.
Treat the fuel system for gasoline with the same respect that you would treat a pressurised propane system. Use the best quality components on every joint and fitting and check them annually or better. No fumes, no boom!
As far as an outboard is concerned, they can be a pain. They put weight where it doesn't belong. Without electric start they are usually in a most awkward place to yank in a rope. They do, however have a couple of advantages over inboards.
1) The prop, etc. spends all of it's time when not spinning out of the water so no marine growth, especially in the tropics.
2) they can be had relatively cheaply, especially two strokes.
3) they work really well in reverse, especially if centered behind the rudder and with the tilt locked down. The prop wash past the rudder allows directional control without sternway, priceless.
4) If you can put an extension handle so that they can be steered from over the pushpit they are magic for tight manouvering.
5) Often they run from portable tanks so that the entire cumbustable thing becomes almost a non issue if the tanks are in a vented cockpit locker.

Just my two cents worth.

Feetup

12-18-2006 01:30 AM

Valiente

Quote:

Originally Posted by Goodnewsboy

As between the two options, a properly managed gasoline inboard engine seems preferable.

Powerboats use gas, cars use gas. Gas isn't the problem, but ignorance can blow you up. Run the blower, make sure the alternator is "marinized" (spark-shielded), double-clamp all hoses, and install a sniffer. Think twice about installing propane, or if it's a small boat, a Coleman stove on a plank in the cockpit plus a rail barbeque running those two-pound bottles seemed to serve us just fine in Toronto where the weather isn't as amenable as Florida.

I have rebuilt and installed an Atomic 4 in my 33 footer and it runs like a charm and is quite economical to boot. I actually REDUCED my gas tankage from 15 to 11 U.S. gallons because I was having trouble using a tank a season. Also, I wanted extra locker space for lines.

Given that I motor off the mooring, get head to wind, and then switch off and get to sailing, that's not surprising. I use about 3/4 gal/hr. at 5.5 knots, which gives me enough range to find a gas station anywhere. If I am motorsailing, I have refuelled enroute from jerrycans, but this is rare.

My new much larger boat has a fat diesel in it and enough tankage for about a thousand NM of range, but it has its own issues, primarily the availability of diesel (and its cleanliness) in certain places, and the fact that diesel engines, unlike gas, really don't enjoy the typical "motor in and out from the basin" scenario. They want to get nice and hot, and so ironically, I am leaving the engine on longer just to warm it up, knowing that the bearings will thank me for not switching it on for just 10 minutes in the cold April air to get beyond the breakwall. So I am burning more diesel than I'd like...because it's a diesel!

This is not a concern with the Atomic 4 anymore than it's a concern with an outboard or a chainsaw. Gas engines can bear short periods of activity. This characterizes a lot of sailboat use...otherwise we'd all have trawlers, right?

11-18-2006 09:29 AM

Goodnewsboy

With respect to a gasoline inboard v. outboard, you will have gasoline in your boat either way. With the inboard, you will likely have a fixed tank and piping. With the outboard, you will probably have a portable tank with hoses.

As between the two options, a properly managed gasoline inboard engine seems preferable.

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